ns3.nameserver.ne.jp has no MX records.
Question and response
Question
dig ns3.nameserver.ne.jp. MX
Answer
The response has no answer records.
Authority
nameserver.ne.jp. 60 SOA nameserver.ne.jp. root.nameserver.ne.jp. 2026022001 3600 1800 604800 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0